Numbers of the BULLETIN
lished at irregular intervals.
essarily completed in any one

OF THE FLORIDA STATE MUSEUM are pub-
Volumes contain about 300 pages and are not nec-
calendar year.

WALTER AUFFENBEUG, Managing Editor
OLIVER L. AusTIN, JR., Editor

Consultants for this issue:
HORACE B. BAKER
HENRY VAN DER SCsAsLE

Communications concerning purchase or exchange of the publication and all
manuscripts should be addressed to the Managing Editor of the Bulletin, Florida
State Museum, Seagle Building, Gainesville, Florida. 32601

Published June 20, 1967

Price for this issue 8.65

THE LAND AND FRESHWATER SNAILS OF
CAMPECHE

FRED G. TnOMPSON'

SYNoPsls.-This review of the land and freshwater snails of Campeche, Mexico,
records 59 species and subspecies of snails including 47 terrestrial and 12 aquatic
forms; 21 are recorded for the first time from the state. Miradiscops haplocochlion
is described as new; 11 previously recognized taxa are placed in synonymy.
Streptostyla, subgenus Chersomitra, is redefined and the soft anatomy of its
type species S. nigricans (Pfeiffer) is described for the first time. Brachypodella
dubia (Pilsbry) is resurrected as a species and distinguished from B. spe!uncae
(Pfeiffer). New descriptions are given for both these species and for Choanopoma
andrewsae (Ancey). Material from adjacent states pertaining to Campeche species
is also included.

'The author is Interim Assistant Curator in Malacology, Florida State
Museum. Most of his researches have dealt with the systematics and zoogeography
of land and freshwater mollusks, with particular emphasis on the American
tropics and Florida. Manuscript received 18 September 1966.

This study is based primarily upon material the author collected
from 24 field stations in Campeche during June 1965, and includes
material he collected from adjacent states that add noteworthy dis-
tribution records for Campeche species. This study also considers
extra-limital species that affect the systematics of Campeche forms.
Campeche is a large state of 50,952 square kilometers in the Yu-
catan Peninsula. The western third is part of the extensive Eastern
Tabasco-Campeche Alluvial Plain; the remainder is formed of low,
rolling karst hills. The state is nearly uniform in its physiography, and
elevations vary from sea level to about 350 meters. The only promi-
nent topographic feature is a short spur of the Sierrita de Tikul.
which rises about 100 meters above the surrounding countryside in
the northern corner of the state (West, 1964: 70-73). The karst de-
velopment allows few permanent bodies of water except in the
western alluvial region. Those that do exist are generally inaccessible.
A climatic transition from northwest to southeast is reflected in the
gradual change from the xeric vegetation along the coast to quasi-
rain forest (Wagner, 1964: 228). For purposes of this study the wet
forests are simply referred to as rain forest.
Terrestrial mollusks have been collected primarily from the karst
regions of the state. Very little material is known from the wetter
alluvial plains, except for a collection Morelet made at Palizada in
1852. Therefore most papers pertaining to Campeche (including this
one) are ecologically biased in their coverage.
No comprehensive report has been made previously on the land
and freshwater snails of Campeche. All early records for the state
appeared as miscellaneous inclusions in various monographs and
faunal reviews. Bequaert and Clench (1933, 1936) summarized what
little was known then and reported a few additions. More recently
Branson and McCoy (1963, 1965) reported on small amounts of ma-
terial collected incidental to other studies. Considering the fragmen-
tary and varied nature of previous contributions, a surprisingly large
number of species have been reported.
Currently 59 species and subspecies of land and freshwater snails
are known from Campeche. Previous workers have reported 47 forms
from the state; 5 of these are of doubtful occurrence in Campeche
and 4 are synonyms of other forms. Material that I collected includes
40 species and subspecies, 21 of which are new records for the state.

THOMPSON: SNAILS OF CAMPECIIE

The following land snails recorded from Campeche are considered
of doubtful occurrence:
Neocyclotus dysoni aureus (Bartsch and Morrison)
Catinella avara (Say)
Euglandina ghiesbreghti (Pfeiffer)
Euglandina sowerbyana (Pfeiffer)
Polygyra oppilata (Morelet)
The following four named forms recorded from Campeche are
now considered synonyms:
Streptostyla maslini Branson and McCoy (= S. meridana)
Streptostyla toltecorum Branson and McCoy (= S. meridana)
Bulimulus inermis (Morelet) (= B. unicolor)
Bulimulus ignavus (Reeve) (= B. unicolor)
Most of the material comprising this study is deposited in the
Florida State Museum at the University of Florida. Representative
specimens are also deposited in the Museo Nacional de Mexico. This
material was supplemented by specimens borrowed from other
museums. Collecting localities are listed from west to east and from
south to north. Records from earlier published reports included in
the species accounts appear in parentheses.
For many helpful suggestions and other courtesies that have aided
in the completion of this study I am indebted to the following people:
Henry van der Schalie and John B. Burch, University of Michigan,
Museum of Zoology (UMMZ); Joseph P. E. Morrison, Harold A.
Rehder and Joseph Rosewater, United States National Museum
(USNM); Tucker Abbott, Academy of Natural Sciences of Philadel-
phia (ANSP); Wayne King, Florida State Museum, University of
Florida (UF). The shell drawings were made by Barbara Weinstein,
Miami, Florida. Field material was collected with the aid of The
National Institutes of Health research grant NIGMS RGB, GM
12300.
GAZETTEER
The following place names in Campeche and Quintana Roo are
cited in the text. Yucatecan place names are on most maps and are
not included.
CAfPECHE
Campeche.-(19' 50' N, 90' 31' W).
Cay6l.-A small village about 27 miles e.s.e. Campeche (19' 45' N,
900 10' W).

The material varies greatly in sculpture and size, and both characters
vary independently. This variation is geographical and not ecological.
I agree with Solem (1961: 201) and Branson and McCoy (1963: 104)
that C. grateloupi (Pfeiffer) is not distinct from C. largillierti.

This species is found in mesic and submesic forested areas, and
apparently is less tolerant of the drier conditions under which C.
largillierti thrives. C. gaigei also shows less tolerance to agrarian dis-
turbances than does C. largillierti. 1 found it only in forests that had
not been recently disturbed.

may be indistinct on old shells. Outer lip and aperture same color as
rest of shell. Early whorls slightly darker. Decollate, 2.8-3.5 whorls
remaining (females, 3.0-3.5; males, 2.8-3.1); 2 embryonic whorls lost
from decollate shells. Apical plug sloping, dorsally flattened, about
Vs whorl long, purplish. Suture deeply impressed. Whorls broadly
inflated, evenly rounded, not shouldered. Umbilicus transversely
oblong due to lateral displacement of aperture; about 1/8-1/10 diame-
ter of last whorl. Aperture adnate to preceding whorl; 0.40-0.49 times
length of shell (females, 0.40-0.46; males, 0.45-0.49); broadly ovate,
1.00-1.09 times as high as wide. Inner lip projecting forward slightly.
Outer lip narrow, of nearly uniform width around aperture; 0.3-0.5
mm. wide or about 1/10-1/15 width of aperture. Upper corner of
outer lip vertical and slightly wider than elsewhere. Outer lip weakly
reflected forward over parietal wall. Sculpture consisting of predomi-
nant axial ribs and very low, broad spiral chords that are most evi-
dent by the wavey appearance that they impart on the ribs, which
are raised and slightly thickened over the chords. Spiral chords most
evident about periphery of whorls and in umbilical region. Axial ribs
abruptly appearing on postembryonic whorls. Initially ribs are widely
spaced and high, but become progressively closer and finer along
spire; ribs finest and closest behind lip. About 10-12 ribs/mm. on face
of last whorl in mature females, 7-8/mm. in mature males. Upper
ends of ribs weakly crenulate along suture. Ribs continuous into
umbilicus as sharp threads. Two embryonic whorls, when present,
elevated and smooth.
Operculum consisting of about 3.5 whorls. Basal chondroid plate
convex. Calcareous lamella broadly reflected over face of chondroid
plate, with its outer edges fused with succeeding turns to form a flat
continuous calcareous plate that completely covers chondroid plate.
Occasionally in specimens from Cozumcl Island some turns of the
lamella may fail to fuse and leave a short, narrow gap between ad-
jacent whorls. Operculum not retractable into adult shell because of
wide calcareous face plate.
Measurements of mainland females: length, 9.2-11.3 mm.; width,
6.8-8.1 mm.; aperture height, 4.0-4.8 mm.; aperture width, 3.9-4.5
mm.
Measurements of mainland males: length, 7.6-8.1 mm.; width,
5.7-6.4 mm.; aperture height, 3.6-3.8 mm.; aperture width, 3.2-3.6
mm.
Measurements for the various insular forms are given by Solem
(1961). My measurements of length and width do not include the

Vol. 11

THOMPSON: SNAILS OF CAMPECHE

outer peristome. The distinction in size between females and males
is not so discrete as the measurements suggest. A few unsexable dead
shells whose measurements are not included fall within the inter-
mediate ranges.
This is a widely distributed and variable species. Insular specimens
tend to be smaller than those from the mainland, but differences of
size and proportions are not constant, even within single populations.
The forms from Cozumel Island (cozumelense) and the mainland
tend to have distinct spiral chords below the suture, while the forms
from the Bay of Honduras (andrewsae and roatanense) usually lack
subsutral chords although spiral chords are usually present in the
umbilical region. The differences between the named varieties are
too slight and variable to justify recognition.
Solem (1961) recognizes the similarities between andrewsae and
cozumelense but contends that the forms are specifically distinct, and
that the similarities are the independent result of convergent evolu-
tion from different mainland species. He postulates that andrewsae
evolved from C. pleurophora (Pfeiffer) and that cozumelense evolved
from C. martensianum (Pilsbry). These assumptions were partially
influenced by his lack of andrewsae material from the mainland. The
wide distribution and variation of andrewsae on the mainland render
untenable his theories on the evolution and relationship of these
forms.
C. andrewsae occurs in mesic and submesic tropical forests. It
may be found with C. largillierti and C. gaigei, although the three
species are ecologically segregated. C. andrewsae inhabits loose rock
piles at a relatively deep level where it is constantly damp and cool.
C. largillierti also occurs in rock piles as well as under scattered rocks,
but usually remains beneath the surface layer of rocks where it is
relatively dry. C. gaigei occurs in leaf mold and debris on the forest
floor, but never under rocks even though it may be found within a
few inches of the other two species.

Specimens from these localities are intermediate between N. d.
berendti and N. d. cooki, and also show intergradation with N. d.
ambiguum. The three subspecies are distinguished on the basis of
color and sculpture. N. d. berendti is dark olivaceous brown or green
with several light spiral lines, and its sculpture is fine, irregular, and
sigmoid but not vermiculated or reticulated. N. d. cooki and N. d.
ambiguum have light brown unicolored shells with strong anasto-
mosing sculpture. In N. d. ambiguun the anastomosing sculpture oc-
curs on the body whorl and the penultimate whorl, whereas in N. d.
cooki it is confined to the body whorl. The specimens listed above are
intermediate between berendti and cooki in sculpture, but only a few
individuals show banding. Some specimens also tend to have anasto-
mosing sculpture on the penultimate whorls, indicating intergradation
with ambiguum. Specimens from 5-11 mi. e. Campeche Branson and
McCoy (1963: 103) recorded as N. d. aurcts (Bartsch and Morrison)
of the Pacific drainage of Oaxaco probably are referable to these inter-
grading forms.
N. d. berendti is confined to the Yucatan Peninsula where it oc-
curs in the states of Yucatan and adjacent areas of Campeche and
Quintana Roo. N. d. cooki is generally distributed in the Peten region
of Guatemala and adjacent parts of British Honduras, Campeche and
Quintana Roo. N. d. ambiguum occurs from northern Chiapas and
Tabasco north and west to central Veracruz. A series of 56 ambiguum
specimens in the U.F. from near San Andres Tuxtla, Veracruz shows
no integraduation with berendti as Solemn (1956: 53) reports.

This species is very rare in Campeche. The only specimen col-
lected was a dead shell.

Helicina amoena Pfeiffer

E. von Martens (1890: 28), recorded this species from Campeche
from specimens collected by Albers. It has not been recorded from
the state since, but may have been overlooked because of its arboreal
habits.

CAMPECHE: (Pantel Aguada, Champot6n; Uluman Savanna, Rio Champot6n.
Bequaert and Clench, 1936: 73).
All the Mexican forms of Pyrgophorus have been referred to P.
coronatus at one time or another. This complex badly needs further
study, which could well show the Mexican forms are recognizably
distinct.

These specimens were collected by shaking small trees and bushes
over a sheet.

SUCCINEIDAE

Succinea carmenensis Fischer and Crosse

CAMPCHEs: (Isla de Carmen. Type locality).

[Catinella avara (Say). Bcquacrt and Clench (1936: 65) recorded this species
from Pantel Aguada, near Champot6n. The record was based on shell material
and must be confirmed, for generic and specific identifications within this family
arc dependent on anatomical and histological data.]

[Euglandina ghiesbreghti (Pfeiffer). Branson and McCoy (1965: 5) record
this and the following species from Champot6n, Campeche. Both are mountain
forms known from limited areas in Chiapas and Oaxaca respectively. The
different ecological and climatic conditions in Campcche make their occurrences
there unlikely. The specimens they cite could not he located to confirm the
identifications.]
[Euglandina sotwerbyana (Pfeiffer). See previous species.]

Euglandina curningi (Beck)

CAMIPECHE: (17.2 mi. s. Chanipot6n. Branson and McCoy, 1965: 4).

Streptostyla

This genus of about 60 species distributed through Central America
and Mexico is divided into five subgenera. These subgenera were
originally defined on the basis of shell characters, but because of the
number and diversity of the species involved, the distinctions be-
tween the subgenera by shell characters is not always clear. Baker
(1941, 1943) redefined three of the subgenera by means of anatomical
characters, but his system of classification is only partially satisfac-
tory because of the small number of species whose anatomies are
known.
The first anatomical studies of Streptostyla were made by Strebel
(1878: 16, 22-23) who described the soft parts of S. streptostyla
(Shuttleworth) (as S. conifornnis), S. nicoleti (Shuttleworth) and S.
physodes (Shuttleworth). Baker .(1943) described the soft parts of
S. streplostyla (genotype of Streptostyla), S. nicoleti (genotype of
Eustreptostyla), S. physodes, S. lymneiformis (Shuttleworth), S. i.
irrigua (Shuttleworth) and S. i. quirozi Strebel. Baker placed S.
physodes and S. lymneiformis in the subgenus Rectoleacirn because
of the similarities of their shells to this otherwise Cuban group. S.
irrigua he placed in Chersomitra because of similarities of its shell to
S. nigricans (Pfeiffer) (genotype of Chersomitra). He separated Cher-
somitra from Streptostyla only as a "section" (= species group) be-
cause of the anatomical similarities of the species he examined.
While studying the relationships of the Campeche species of
Streptostyla, I dissected two specimens of S. nigricans to verify the
identity of Chersomitra. The characters of the epiphallus and penis
proved similar to those Baker described for S. physodes and S. lynm-
neiformis, and quite different for those he reported for S. irrigua. This
necessitates the following systematic changes: (1) Chersomitra in-

BULLETIN FLORIDA STATE MUSEUM

eludes S. nigricans, S. physodes and S. lymneiformis, and is used in
place of Rectoleacina for mainland species. (2) Streptostyla includes
S. streptostyla and S. irrigua as well as S. ventricosula (Morelet) and
S. meridana (Morelet) as discussed below. (3) The subgeneric relation-
ships of most of the other species of Streptostyla usually placed in the
typical subgenus or Chersomitra remain uncertain, for convergent
evolution in shell characters has occurred in both groups. (4) Rect-
oleacina is again restricted to Cuba, and its anatomy and relationships
to mainland taxa remain unknown.
The subgenera that are known anatomically may be distinguished
as follows:
Streptostyla: epiphallus absent; penis simple, without accessory
appendages; salivary gland forming a complete ring around the
esophagus.
Eustreptostyla: epiphallus present; penis simple, lacking accessory
appendages; a "stimulator" presents on inside of penis wall; salivary
gland incomplete across ventral surface of esophagus.
Chersomitra: epiphallus present; penis with a single lateral ap-
pendage; salivary gland forming a complete ring around the esopha-
gus.
Peteniella and Streptostylella are still unknown anatomically.

Streptostyla nigricans (Pfeiffer)

CinArAs: 3.5 mi. s. Ray6n, 5500' (two specimens dissected).

Sides of foot and snout bright yellow bordered dorsolaterally on
each side of body by a broad black band that is continuous over dosal
surface of tail. Nape with a narrow bright yellow middorsal stripe that
is continuous to snout. Mantle collar dull yellow. Outer wall of lung
black fading into dark brown near collar. Rest of mantle light pinkish
yellow.
Tail pointed, rounded above, without distinct pedal groove. Lung
about twice as long as wide. Minor venations of lung distinct. Kidney
T-shaped, almost triangular (fig. 1, F). Pericardium about 0.8 times
length of kidney base. Esophagus entering dorsal side of buccal bulb
anterior to radula. Salivary gland continuous around esophagus (fig.
1, A). Right occular retractor muscle passing through genital atrium.
Genital atrium connected to body wall by a relatively long slender
neck (fig. 1, C). Ovotestis consisting of six lobes with 3-9 alveoli per
lobe (not illustrated). Spermatheca pressed against uterus by aorta,

Vol. 11

THOMPSON: SNAILS OF CAMPECHIE

and resting behind prostate. Albumen gland bright orange in color,
very large, elongate, sausage-shaped with a broad furrow in baso-
columellar side where it rests against intestine. Prostate relatively
large, about % length of uterus and closely appressed; located near
top of enlarged uterine folds. Vas deferens enlarged into an epiph-
allus about half way between prostate and penis. Penial retractor
muscle long and slender, attached to diaphram over salivary gland,
enveloping epiphallus for a short distance above penis. Penis long
and moderately stocky, with a large diverticulum located about /4
of distance below epiphallus. Inside of diverticulum with numerous
oblique longitudinal folds. Inside of penis with large opposing longi-
tudinal ridges.
Radula (one specimen examined) containing 60 transverse rows
of teeth, with 56 teeth per row. Inner tooth longest, or only slightly
shorter than next tooth, about 175 1 long. Following teeth gradually
decreasing in size through outer marginal tooth, which is about 30 p,
long. Cusps on teeth simple, dagger-shaped. Ribbon 7.6 mm. long.
Although fundamentally similar in anatomical characters to S.
physodes and S. lymneiformis, S. nigricans is very distinct from these
two species by the large size of its albumen gland and by the long
neck that connects the genital atrium to the body wall. The extension
of the right occular retractor muscle through the genital atrium in
S. nigricans has not been recorded from other species of Streptostyla.

This species is found most commonly in semi-arid and mesic habi-
tats, where it occurs in second growth as well as virgin forests. Only
rarely is it found in rain forests.
S. meridana was adequately described and illustrated by Pilsbry
(1907: 154-155; pl. 30, figs. 93-96). My measurements of 50 specimens
from Campeche, Quintana Roo, and Yucatan are: length, 8.2-10.4 mm.;
width, 3.4-4.3 mm.; length of aperture, 4.8-6.1 mm.; length/width,
2.27-2.48; length/aperture, 1.59-1.73; 4.6-5.5 whorls.
Streptostyla maslini Branson and McCoy and Streptostyla tolte-
corum Branson and McCoy do not differ from typical S. meridana
(Morelet). The measurements and proportions given by Branson and
McCoy (1962: 8-9) fall within the ranges of variation for S. meridana
given by Pilsbry (1907: 154-155), and which I have found in my popu-
lation samples. Branson and McCoy's illustrations have little similarity

Vol. 11

THOMPSON: SNAILS OF CAMPECHE

to the type specimens they represent. Figures of these same specimens
(fig. 2, A-D) drawn with the aid of a camera lucida fall well within
the variations illustrated for S. meridana by Pilsbry (1907: pl. 30, figs.
93-96).
Branson and McCoy originally assigned their material in manu-
script to Salasiella meridaensis new species, and Salasiella toltecorum,
new species. After they had deposited their material in various

museums under their manuscript names, they realized their specimens
belonged in the genus Streptostyla. In their descriptions (1962) of S.
maslini and S. toltecorum they apparently did not compare this ma-
terial adequately with all the numerous forms of Streptostyla.
Two specimens dissected from 5.1 mi. n.n.w. Dzibalchen are
similar to S. streptostyla except: Animal uniformly light gray. Lung
unmarked, uniformly gray. Kidney triangular, about twice as long as
oblique base. Pericardium about 0.6 times length of kidney. Salivary
glands continuous around esophagus. Right occular retractor muscle
passing inside from genitalia. Genital atrium attached directly to
body wall, without a connecting neck (fig. 1, II, I). (Only female
half'of system illustrated because penis of each dissected specimen
was -everted and not in usual position). Spermatheca columellar, im-
bedded at base of albumen gland. Albumen gland elongate sausage-

BULLETIN FLORIDA STATE MUSEUM

shaped, slightly compressed. Prostrate about % length of uterus, re-
stricted primarily to outer surface, and middle of uterus. Vas deferens
slightly enlarged near middle. Penial retractor muscle attached to
inner wall of diaphram, enveloping vas deferens for about % of mus-
cle length. Penis long, moderately stocky, without accessory appen-
dages or stimulator.
Radula (1) containing 45 transverse rows of teeth, with 40 teeth
per row. Inner tooth about 75 Ip long. Following three teeth rapidly
increasing in size. Fourth tooth about 110 a long. Remaining teeth
gradually decreasing in size through last tooth, which is about 14 t
long. Ribbon 3.7 mm. long.
The characters of the reproductive system show this species is
closely related to S. ventricosula. Anatomically it differs from this
species in its proportionally larger prostrate, which is located primar-
ily on the outer surface of the uterus.

This species is most similar to M. maya (Pilbsry), but differs by its
whitish color, by having a relatively larger umbilicus, and by having
a depressed conical spire. M. maya is pale yellow in color, has an
umbilicus that is contained slightly more than 4 times in the major
diameter, and has a depressed dome-shaped spire. The latter species
is also smaller and has only four whorls, but this may be only a matter
of individual sizes (Pilsbry, 1919: 216).
I name this species with some hesitation, but its whitish color
and larger umbilicus do not allow it to be identified with any of the
other named species of Miradiscops.
The type specimens were found under a broken block of caliche
near a black mangrove swamp.

ZONITIDAE

Habroconus pittieri (von Martens)

CArI'ECHE: 5.1 mi. n.n.w. Dzibalch6n; 8.1 mi. s.w. Champot6n; 7.2 mi. s.
Pixt6n; 19.2 mi. e. Silvituc.
QUINTANA Roo: 4.0 mi. e. Xpujil, Campeche; 7.1 mi. n.n.w. Xiatil.
YUCATAN: 0.8 mi. n.e. Becanchbn.
These specimens are similar in all characters of the description
and illustrations given by von Martens (1892: 121), except that they
have slightly finer sculpture. In this respect they are similar to H.
elegantula (Pilsbry), but the spire is not as high nor do they have as
many whorls as that species.

CAMPECHE: 8.1 mi. s.w. Champot6n; 7.2 mi. s.w. Pixtin.
The specimens from Campeche are slightly more obese than any
of the subspecies described from farther north, but my material is
inadequate to determine the geographical distribution of this varia-
tion.

This highly plastic species undergoes considerable geographic
and ecological variation that has resulted in at least five synonyms.

Vol. II

1967 THOMPSON: SNAILS OF CAMPECHE 245

The group was most recently reviewed by Pilsbry (1897: 50-58), who
presented descriptions, based upon type material, of all of the forms
named at that time. These forms may be briefly diagnosed as follows:
B. unicolor a medium sized, conical form, 14-19 mm. long with
about 5-6 whorls, weak incremental sculpture, no spiral sculp-
ture, and a thin shell with a corneous-brown periostracum.
B. umbraticus similar to B. unicolor, but transparent white
streaked with pale brown near the apex.
B. ignavus similar to B. unicolor, but a small form about 9 mm.
long, and with about 7 whorls (?).
B. petenensis similar to B. unicolor, but with alternating light
and dark streaks on the periostracum.
B. sanmiguelensis similar to B. unicolor, but with nearly flat
whorls united by a relatively superficial suture.
Since they were originally proposed, these named forms have been
assigned to different taxonomic ranks by various authors. Pilsbry
(1897: 50-58) followed previous authors in his treatment of this group.
He recognized unbraticus as a separate species, petenensis as a
geographic race of unicolor, and ignavus as a "variety" of B. dysoni
(Pfeiffer), though doubtfully so. More recently Richards (1937: 253-
254) described sanmiguelensis, and Harry (1950: 12-15) elevated
ignavus to specific status.
Material I have examined indicates that the size of the shell varies
with the climatic areas of the Yucatan Peninsula as follows (fig. 4):
Dry coastal areas of Campeche and Yucatan, and the Polochic Val-
ley of Guatemala (ignavus) size small, 9.0-10.0 mm. long,
0.50-0.62 times as wide as long; aperture 0.44-0.58 times
length of shell; 4.3-5.1 whorls.
Mesic deciduous forests of Campeche and Yucatan (inter-
mediate sized form) 10.0-12.6 mm. long; 0.56-0.64 times as
wide as long; aperture 0.45-0.57 times length of shell;
4.7-5.7 whorls.
Moist deciduous and evergreen forests of Yucatan, Quintana Roo,
British Honduras and Peten unicolorr, petenensis) modera-
tely large forms 12.3-16.5 mm. long; 0.48-0.69 times as wide
as long; aperture 0.45-0.52 times length of shell; 5.5-6.1
whorls.
Wet rain forests of Quintana Roo and British Honduras (uni-
color, sanmiguelensis) size large, 14.8-18.7 mm. long; 0.48-0.59

BULLETIN FLORIDA STATE MUSEUM

times as wide as long; aperture 0.44-0.51 times length of
shell; 5.5-6.3 whorls.

Distinctions based on size between any of these forms are not
tenable because of the continuous series of intergradations that occur
(fig. 5). There is still some question about the identity of Bulimus

O 9.0-10.0 mm.
* 10.0-12.6 mm.
A 12.3-16.5 mm.
* 14.8-18.7 mm.

0

--
- -

0 -
AA ;A

i
I I I

A

I t S

Ai
- - - - - - - -

FIGmrE 4. The geographic distribution of Bulimulus unicolor (Sowerby) in the
Yucatan Peninsula and adjacent areas, showing the distribution of
size forms throughout the region. Open circles represent a small form
9.0-10.0 mm. long. Solid circles represent a larger form 10.0-12.6
mm. long. Triangles represent a larger form 12.3-16.5 mm. long.
Squares represent large specimens 14.8-18.7 mm. long.

Vol. 11

THOMPSON: SNAILS OF CAMPECHE

3.'

.5
I-..

S .*

.. ." r"

% ,

0 9 10 II 12 13

14 15 16 17

LENGTH of SHELL
FicuRE 5. Graph showing the relationships between the length of the shell, and
the width of the shell, the length of the aperture and the number of
whorls in Bulimulus unicolor (Sowerby). No breaks in the trends oc-
cur that would allow the recognition of more than one form on the
basis of these ratios.

18 19

BULLETIN FLORIDA STATE MUSEUM

ignacus. In his original account Reeve (1849) stated that it had seven
whorls, but no specimen corresponding to its size has subsequently
been found with as many whorls. Harry (1950: 13) apparently worked
on the assumption that Reeve's short description and figure were in
error or that the type was based upon an abnormal specimen, and
assigned the small form discussed above to ignavus. B. petenensis
appears to be only a geographic color variation of unicolor, and is
confined to the Peten region of Guatemala. Some populations found
in the same region consist entirely of the form unicolor, and most
series of petenensis also have some specimens that can be identified
as unicolor. B. umbraticus appears to be only an extreme variation of
the petenensis color form. The characteristic of the flat whorls that
Richards used to separate B. sanmiguelensis is also untenable, for this
character varies widely among different series of specimens from over
the whole range of the species.
Bulimus inermis Morclet, 1851, is probably also synonymous with
B. unicolor. The type specimen is 9.0 mm. long, 4.0 mm. wide, has an
aperture 3.0 mm. long, and 7 whorls (Fischer and Crosse, 1878: 550).
A single specimen that I collected from 7.0 mi. s.s.e. Uman, Yucatan,
and two specimens from Tabasco (USNM 10555) approach these pro-
portions, but do not have as short an aperture or as many whorls.
B. unicolor may be properly diagnosed as follows: a highly varia-
ble Central American species of the subgenus Bulimulus, 9.0-18.7
mm. long; 0.48-0.63 times as wide as long; aperture 0.44-0.56 times
length of shell; 4.9-6.3 whorls; postembryonic sculpture consisting of
incremental striations only; generally unicolor or various hues of
brown, but may be streaked or shaded; aperture oblique, but nearly
straight edged in lateral profile.
This species probably intergrades with B. corneus (Sowcrby)
which occurs farthur south but sufficient material from Guatemala
and Honduras to determine this is not available.

QUINTANA Roo: 4.0 mi. e. Xpujil.
YUCATAN: 0.8 mi. n.e. Becanch6n; 19.1 mi. s.s.c. Uman.
This species appears to be common in semi-mesic, mesic and rain
forests within its range. It is an abundant snail, judging from the
number of dead shells in recently cleared areas.

to apical plug, 10.0-12.3 mm.; width of shell, 2.0-2.3 mm.; width of
aperture including peristome, 1.6-2.0 mm.
The number of ribs on the lower whorls is variable. Though char-
acteristic of different populations, the variation shows no geographic
or ecological pattern. Other features of the sculpture and the structure
are nearly constant.
B. dubia is similar to and may be only subspecifically distinct
from B. speluncae, with which it has been confused. It is distinguished
by its low number of whorls below the apical plug, by its low number
of ribs per whorl, by its strong, low axial ribs, by its elongate cylindric-
conical shape and by its narrow peristome.
This species has been confused with B. speluncae because of the
lack of comparative material of the latter species in American collec-
tions. Pilsbry (1891: 316) recognized Cylindrella speluncae var. dubia
on the bases of an aberrant population of small individuals from
Labna, Yucatan. Later (1904: 70) he relegated dubia to the synonymy
of speluncae because of a lack of satisfactory differences between
dubia and other Yucatan populations of Brachypodella that he identi-
fied as speluncac. All subsequent authors followed this 1904 usage of
the name speluncac. Large series of B. speluncae Henry van der
Schalie collected in 1936 from the Petcn is the first material of that
species collected since Morelet visited the area. The material permits
a redescription of that species, which warrants the recognition of B.
dubia as a distinct species.

This species is known only from a small area in Peten. Records
outside this area refer to B. dubia (Pilsbry).
Shell dull, light beige; inside of aperture and peristome shiny
white. Impcrforate. Thin, nearly translucent. Elongate-turrete; widest
at about the fourth or fifth from last whorl and tapering below. Spire
very attenuate when complete. 21.2-23.6 whorls in adults with com-
plete spires. Shell usually decollate at maturity; 13.0-14.6 whorls be-
low apical plug. Whorls moderately convex; periphery above middle
of whorl. Aperture extending forward and down on a long neck that
is about as long as diameter of shell. Neck with a strong basal ridge.
Aperture subcircular, with a broad flaring peristome that is about 2
the width of the aperture. Peristome widest in baso-columellar
region; 0.40-0.55 mm. wide along columellar margin. Aperture weakly
angulate in lower and outer margins; 3 rounded embryonic whorls
that are nearly uniform in size. Second embryonic whorl 0.5-0.6 mm.
wide. Embryonic whorls sculptured with fine, regularly spaced axial
threads that are about 0.05 mm. apart. Following whorls gradually
increasing in size. Sculptured with numerous axial ribs that are nearly
uniformly spaced over the surface of shell. 21-31 ribs on antipenulti-
mate whorl. Ribs weakly sigmoid and slightly oblique; very thin and
relatively high, about 3-4 times as high as wide. Ribs slightly thickened
and raised near lower suture. Internal axis thin, rounded, weakly
spiral.
Length of complete shell, 14.7-16.2 mm.; length of shell below
apical plug, 10.7-13.3 mm.; width of shell, 2.0-2.4 mm.; width of aper-
ture including peristome, 1.7-2.2 mm.
B. speluncae is conservative in variation. The sample gathered
from beach drift along the west shore of Lago de Petenxil is unusual
in that some stunted specimens have as few as 9.0 whorls.
This species is distinguished by its large number of whorls below
the apical plug, by its thin, high sigmoid ribs, by its elongate-turret
shape, by its large number of ribs per whorl, and by its wide peris-
tome. Available material from Peten and the Yucatan Peninsula shows
no intergradation in these characters with B. dubia.

CAMPECHE: (Isla de Carmen. Fischer and Crosse, 1872: 277).
[Polygyra oppilata (Morelet). Bequaert and Clench (1933: 532) restricted the
type locality of this species to Campeche ("Littora Yucatanea"). No Campeche
material is on record, and the species is known only from northern Veracruz and
adjacent regions of Tamaulipas and San Luis Potosi.]

All these species of Thysanophora are arboreal. Live specimens
are difficult to find because of their minute size, but they can be col-
lected in large numbers by shaking small trees and bushes over a
sheet.

Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM may be in any
field of biology. Manuscripts dealing with natural history or systematic problems
involving the southeastern United States or the Caribbean area are solicited
especially.
Manuscripts should be of medium length-50 to 200 pages. Examination for
suitability is made by an Editorial Board.
The BULLETvI is distributed worldwide through institutional subscriptions and
exchanges only. It is considered the responsibility of the author to distribute his
paper to all interested individuals. To aid in this, fifty copies are furnished the
author without cost.

PREPARATION OF MANUSCRIPT
Highly recommended as a guide is the volume:

Conference of Biological Editors, Committee on Form and Style.
1964. Style manual fur biological journals, 2nd ed.
Amer. Inst. Biol. Sci., Washington. ix-117 pp.
Manuscripts should be typewritten with double spacing throughout, with ample
margins, and on only one side of the paper. The author should keep a copy; the
original and a carbon must be submitted. Tables and legends of figures should
be typed on sheets separate from the text. Several legends or tables may be
placed on a single sheet.
Illustrations, including maps and photographs, should be referred to as "figures."
All illustrations are reduced to a maximum of 4-1/4 by 7-1/8 inches. Size scales,
wherever they are necessary, should be incorporated into the figure.
References to literature should conform with the bibliographic style used in recent
numbers of the BULLETIN. Spell out in full the titles of non-English serials and
places of publication.
Footnote material should be kept to a minimum. However, provide copy for a
footnote detailing the title, affiliations, and address of the author (see recent
numbers of the BULLETIN).
Manuscripts must be accompanied by a synopsis-a brief and factual summary
(not a mere description) of the contents and conclusions, which points out the
presence of any new information and indicates its relevance. In it list all new
organisms described and give their ranges; indicate all taxonomic changes pro-
posed. The synopsis, written in full sentences, should be concise, but completely
intelligible in itself without references to the paper, thereby enabling the busy
reader to decide more surely than he can from the title alone whether the paper
merits his reading. The synopsis will be published with the paper. It does not
replace the usual conclusions or summary sections. It may also serve as copy
for the abstracting services.
Manuscripts and all editorial matters should be addressed to:

Managing Editor of the BULLTIrN
Florida State Museum
Seagle Building
Gainesville, Florida